Session 3: The Nose and Paranasal Sinuses; The External and Middle Ear Flashcards
What is the external nose composed of?
Partly of bone and partly of hyaline cartilage, with the nasal bones meeting in the midline superiorly.
Where do the nasal bones meet?
Superiorly in the midline
What forms the lower boundary of the external nose?
The meeting of the two maxillae
What forms the lateral boundary of the external nasal aperture (naris)?
Fibrofatty tissue posteriorly and major alar cartilage anteriorly.
What forms the medial boundary of the aperture of the external nose below the nasal septum?
The major alar cartilages turning inwards
What is the vestibule of the nose?
The short distance into the nose into which the hairy skin of the external nose extends
What divides the nasal cavity into right and left halves?
Nasal septum
What forms the medial wall of each nasal cavity?
Nasal septum
What is attached to the nasal septum superiorly?
Perpendicular plate of the ethmoid
What is attached to the nasal septum posteriorly?
Vomer
What is attached to the nasal septum anteriorly?
Major alar cartilage
What forms the roof of the nasal cavity?
Anteriorly - Nasal bones
Middle - Cribiform plate of ethmoid
Posteriorly - Inferior surface of the body of the sphenoid
What passes through the cribiform plate of the ethmoid?
Olfactory nerves to reach the olfactory bulb
What forms the floor of the nasal cavity?
Anteriorly - Palatine processes of maxillae
Posteriorly - Horizontal plates of palatine bones
What forms the lateral walls of the nasal cavity?
Maxillae + 3 conchae
What bones are the superior, middle and inferior conchae part of?
Superior + middle = part of ethmoid
Inferior = separate bone
Describe the conchae.
Large, medially-directed bony elements covered by highly vascular mucous membranes. On the lateral walls of the nasal cavity.
What is the action of the conchae?
To heat and humidify air that passes them during breathing
Where are the meatuses in relation to the conchae?
Beneath each shelf like conchae
What opens into the meatuses?
Paranasal sinuses
Which paranasal sinus opens into the superior meatus?
Posterior ethmoidal
Which paranasal sinuses open into the middle meatus?
Maxillary, frontal, anterior ethmoidal, middle ethmoidal
What opens into the inferior meatus?
Nasolacrimal duct
Where does the sphenoidal sinus open?
Sphenoidal recess posterior to the superior conchae/meatus
Where does the Eustachian tube open?
The lateral wall of the nasal cavity, posterior to the inferior conchae/meatus.
Which arteries supply the nasal cavity? (4)
FROM ECA: - sphenopalatine artery (maxillary) - ascending branch greater palatine (maxillary) - labial (facial artery) FROM ICA: - anterior ethmoidal (opthalmic)
Which veins does the venous blood drain into?
Facial, opthalmic and sphenopalatine veins.
What do the sphenopalatine veins form?
Pterygoid plexus of veins in the infratemporal fossa
Where is the olfactory mucous membrane located? What is it responsible for?
Roof and adjacent parts of medial and lateral walls, smell
Which epithelium covers the olfactory mucous membrane?
Columnar epithelium
Which epithelium covers the vestibule?
Stratified squamous epithelium
Which epithelium covers the nasal cavity? (not vestibule or olfactory mucous membrane)
Respiratory epithelium
What is general sensation in the nasal cavity mediated by?
Branches of Va and Vb
What is the parasympathetic secretomotor supply to the nasal cavity?
Greater petrosal (VII) –> pterygopalatine ganglion –> branches of Vb
Which epithelium lines the paranasal sinuses?
Ciliated mucous columnar epithelium
How are the ciliary currents directed?
Spirally towards the opening of the sinuses
Where does the frontal sinus lie?
Above the orbit
Where does the frontal sinus enter the nasal cavity?
Anterior end of middle meatus
Describe the maxillary sinus. Where does it lie?
Large, occupies most of the maxilla
Lies lateral to the nasal cavity, above the upper molar teeth. Its floor extends to a lower level than the floor of the nasal cavity.
Describe the opening of the maxillary sinus.
It is above the level of the floor of the maxillary sinus. It drains into the middle meatus
Describe the ethmoidal sinuses.
Small, interconnected air cells which lie between the orbit and nose. Divided into 3 cavities: anterior, middle and posterior.
What is the name given to the prominent bulge on the lateral wall of the nose?
Bulla of the ethmoid
Where are the middle ethmoidal air cells located?
In the bulla of the ethmoid
What lies beneath each bulla?
A curved opening, the hiatus semilunaris
What lies within the hiatus semilunaris?
The openings to the frontal and maxillary sinuses, the anterior ethmoidal air cells
Where do the posterior ethmoidal air cells open?
The superior meatus.
Where do the anterior and middle ethomidal air cells open?
The middle meatus.
What are important relations to the sphenoidal air sinus?
Pituitary gland superiorly
Cavernous sinus laterally
Where does the sphenoidal sinus open?
Small, triangular space just above the superior concha known as the sphenoidal recess.
What is the function of the paranasal sinuses?
Resonance chambers during speech
Lighten bones of facial skeleton
What are the divisions of the ear?
External ear, middle ear, internal ear.
What does the auricle consist of?
Elastic cartilage covered with skin, with ridges and depressions.
What lies anteriorly to the EAM opening?
Tragus
What lies posteriorly to the EAM opening?
Concha
What is the outer edge of the auricle known as?
Helix
What is the inferior projection of the auricle known as? What is it formed by?
Lobule, fibrofatty tissue
Where does the EAM extend from and to? How long is the EAM?
From the concha of the auricle to the tympanic membrane, 3cm long.
What is the lateral 1/3 of the EAM formed by? Which structure is it continuous with?
Cartilage, the auricle.
Where in the lateral 1/3 is the EAM deficient? What is it completed by?
Posterosuperiorly, fibrous tissue
What is the medial 2/3 of the EAM formed by?
Bone
Where is the tympanic membrane attached?
A groove around the sides and floor of the medial EAM.
What is another name for the middle ear?
Tympanic cavity
Where is the middle ear located?
Hollowed-out cave in the petrous temporal bone.
What forms the roof of the tympanic cavity? What does the roof separate the tympanic cavity from?
Plate of bone; separates the middle ear from the middle cranial fossa, meninges and temporal lobe of the brain
What forms the floor of the tympanic cavity? What does it separate the tympanic cavity from?
Thin plate of bone; jugular fossa (which houses the IJV and carotid canal)
What forms the lateral wall of the tympanic cavity?
Tympanic membrane (also pars flaccida and cone of light), handle of malleus
Describe the tympanic membrane.
Forms lateral wall of tympanic cavity, inserted into groove in bony portion of EAM, placed obliquely downwards and medially, bulges into the middle ear so that its lateral surface is concave.
Which surface of the tympanic membrane is the handle of the malleus attached to?
Medial surface.
What is the thin and loose part of the tympanic membrane known as?
Pars flaccida
What forms the medial wall of the tympanic cavity?
Oval window, promontory
Where does the oval window lead?
Internal ear
Describe the promontory. What is it formed by?
Bulge in the medial wall of the tympanic cavity, produced by the first turn of the cochlea.
Where does the facial nerve run in the middle ear?
It enters in the facial canal in the medial wall of the tympanic cavity. On reaching the posterior wall of the tympanic cavity, the nerve runs inferiorly to emerge from the skull at the stylomastoid foramen.
Name the 3 auditory ossicles of the middle ear.
Malleus, stapes, incus
What is the function of the ossicles?
They articulate with each other to transmit vibrations of the membrane to the internal ear.
Describe the malleus
Has a LATERAL PROCESS and HANDLE which are attached to the tympanic membrane
Has a rounded SUPERIOR HEAD which articulates with the body of the incus
How does the malleus articulate with the incus?
It’s superior head articulates with the body of the incus.
How does the incus articulate with the stapes?
Via its long process
Where is the base of the stapes located?
In the oval window.
What is the function of the base of the stapes?
Movement of the base of the stapes causes vibration of the fluid in the internal ear, stimulating its auditory receptors
Where is the tensor tympani attached?
Malleus
Where is the stapedius muscle attached?
Stapes
What is the tensor tympani supplied by?
Nerve to medial pterygoid (Vc)
What is the stapedius muscle supplied by?
Nerve to stapedius (VII)
What is the action of the tensor tympani and stapedius muscles?
Act to modify the transmission of sound waves
What does the Eustachian tube connect?
The anterior wall of the tympanic cavity to the lateral wall of the nasopharynx.
Describe the Eustachian tube.
It has a medial cartilagenous part and a lateral bony part.
What is the role of the Eustachian tube?
It allows air to enter or escape from the middle ear in order to equalise pressure between the tympanic cavity and the external environment.
What does the aditus connect?
The posterior wall of the tympanic cavity with the mastoid antrum, a hollow air-filled cavity.
Describe the growth of the mastoid antrum during development.
It is small at birth but enlarges as the mastoid process enlarges.
What are the relations of the mastoid antrum?
Separated from the posterior cranial fossa (containing the cerebellum and sigmoid sinus) by a thin plate of bone.
Superiorly related to the temporal lobe of the brain.
What is the blood supply to the middle ear?
Branches of the internal carotid and maxillary arteries.
What is the innervation of the middle ear?
Glossopharyngeal nerve (IX) through the tympanic plexus
Where does the facial nerve give off the greater petrosal nerve?
At the geniculate ganglion in the facial canal.
What does the internal ear contain?
Sense organs for balance and hearing. Osseous labyrinth (with vestibule, semicircular canals and cochlea) which contains the membranous labyrinth
Where are the utricle and saccule located?
In the vestibule of the osseous labyrinth.
What are the utricle and saccule responsible for?
Static equilibrium
Where are the semicircular ducts located?
In the semicircular canals
What are the semicircular ducts responsible for?
Dynamic equilibrium
What is the cochlear duct?
The organ of hearing
What is the internal ear supplied by?
Vestibulocochlear nerve (VIII)